Generally, a construction machine (working machine) such as a hydraulic shovel and so on is composed of, as shown in FIG. 3, an upper revolving unit 102, a lower traveling unit 100 and a working apparatus 118.
The lower traveling unit 100 includes a right track 100R and a left track 100L which can be driven independently of each other. Meanwhile, the upper revolving unit 102 is provided for revolving movement in a horizontal plane with respect to the lower traveling unit 100.
The working apparatus 118 is principally composed of a boom 103, a stick 104, a bucket 108 and so forth, and the boom 103 is mounted for pivotal motion with respect to the upper revolving unit 102. Further, the stick 104 is connected for pivotal motion similarly in a vertical plane to an end of the boom 103.
A boom driving hydraulic cylinder (boom cylinder) 105 for driving the boom 103 is provided between the upper revolving unit 102 and the boom 103, and a stick driving hydraulic cylinder (stick cylinder) 106 for driving the stick 104 is provided between the boom 103 and the stick 104. Further, a bucket driving hydraulic cylinder (bucket cylinder) 107 for driving the bucket 108 is provided between the stick 104 and the bucket 108.
By such a construction as described above, the boom 103 is constructed for pivotal motion in an a direction and a b direction in the figure and the stick 104 is constructed for pivotal motion in a c direction and a d direction in the figure, and the bucket cylinder 107 is constructed for pivotal motion in an e direction and an f direction in the figure.
FIG. 4 is a view schematically showing a construction of essential part of a hydraulic circuit of such a hydraulic shovel as described above. As shown in FIG. 4, traveling motors 109L and 109R as power sources which are independent of each other are provided for the left track 100L and the right track 100R described above, respectively, and a revolving motor 110 for driving the upper revolving unit 102 to revolve with respect to the lower traveling unit 100 is provided for the upper revolving unit 102.
The traveling motors 109L and 109R and revolving motor 110 mentioned above are constructed as hydraulic motors which are operated by a hydraulic pressure, and working oil of a predetermined hydraulic pressure is supplied to them through a hydraulic pump driven by an engine (principally by a Diesel engine) not shown or a hydraulic control circuit apparatus 111 shown in FIG. 4.
In response to a working oil pressure supplied in this manner, the hydraulic motors 109L, 109R and 110 are driven. Also the cylinders 105 to 107 are driven by the hydraulic pressure from the hydraulic pump driven by the engine not shown in a similar manner as described above.
An operator cab 101 includes, as operation members for controlling operation of the hydraulic shovel (traveling, revolving, pivotal motion of the boom, pivotal motion of the stick and pivotal motion of the bucket), a left lever 101B, a right lever 101C, a left pedal 101L, a right pedal 101R and so forth.
When, for example, an operator operates the lever 101B or 101C and/or the pedal 101L or 101R, the hydraulic control circuit apparatus 111 is controlled so that a suitable one or ones of the cylinders 105 to 107 and the hydraulic motor 109L, 109R and 110 are driven. As a result of the driving, the upper revolving unit 102 can be revolved, or the boom 103, stick 104, bucket 108 and so forth can be pivoted, or the hydraulic shovel can be driven to travel.
By the way, as shown in FIG. 4, the hydraulic control circuit apparatus 111 includes hydraulic control valves (main control valves) 111-1 to 111-6 for adjusting control amounts of the cylinders 105 to 107 and the hydraulic motors 109L, 109R and 110, respectively.
Here, all of the main control valves 111-1 to 111-6 are 3-mode directional control valves having three modes of neutral, extension (forward operation) and contraction (reverse operation), and operation conditions thereof are changed over by pilot hydraulic pressures supplied thereto via pilot fluid paths 112-1 to 112-6, respectively.
The fluid paths 112-1 to 112-6 are mechanically connected to the operation members (levers and pedals) 101B, 101C, 101L and 101R via remotely controlled valves 14-1 to 14-6.
In order, for example, to move the boom 103 upwardly (in the a direction in FIG. 3) from its stopping condition, an operator will operate the right lever 101C to change over the remotely controlled valve 14-1 to change over the feeding condition of the pilot hydraulic pressure in the pilot fluid path 112-1. Consequently, the pilot hydraulic pressure acts in a desired condition upon the control valve 111-1 so that the control valve 111-1 is changed over from the neutral mode to the extension mode.
After the control valve 111-1 is changed over into the extension mode in this manner, the working oil pressure from the hydraulic pump is supplied to a pressure chamber of the boom cylinder 105 on the lower side in the figure through fluid paths 113-1 while the working oil in another pressure chamber of the boom cylinder 105 on the upper side in the figure is drained so that the boom cylinder 105 is extended.
Similarly, the control valve 111-2 is changed over by the pilot hydraulic pressure supplied thereto by an operation of the right lever 101C. This pilot hydraulic pressure is supplied through the pilot fluid paths 112-2, and when the control valve 111-2 is changed over by an action of this pilot hydraulic pressure, the feeding condition of the working oil from fluid paths 113-2 to the bucket cylinder 107 is controlled. Consequently, the bucket cylinder 107 is driven to be contracted to drive the bucket 108.
Further, the control valve 111-3 is changed over by the pilot hydraulic pressure supplied thereto by an operation of the left pedal 101L. This pilot hydraulic pressure is supplied through the pilot fluid path 112-3, and when the control valve 111-3 is changed over by an action of this pilot hydraulic pressure, the feeding condition of the working oil from fluid paths 113-3 to the left side traveling motor 109L is controlled. Consequently, the driving condition of the left side traveling motor 109L is controlled (that is, the speed of rotation is controlled) to control the driving condition of the left track 100L.
On the other hand, the hydraulic control valve 111-4 is changed over by an operation of the right pedal 101R, and the driving condition of the right side traveling motor 109R is controlled by an action similar to that of the control valve 111-3 described above.
Furthermore, the control valve 111-5 is changed over by the pilot hydraulic pressure supplied thereto by an operation of the left lever 101B. This pilot hydraulic pressure is supplied through the pilot fluid path 112-5, and when the control valve 111-5 is changed over by an action of the pilot hydraulic pressure, the feeding condition of the working oil from a fluid path 113-5 to the revolving motor 110 is controlled. Consequently, the driving condition of the revolving motor 110 is controlled to drive the upper revolving unit 102 to revolve.
On the other hand, the control valve 111-6 is changed over by the pilot hydraulic pressure supplied thereto by an operation of the left lever 101B and acts in a similar manner to the control valves 111-1 and 111-2 described above. Then, by changing over the control valve 111-6, the hydraulic pressure to act upon the stick cylinder 106 can be controlled to control the driving condition of the stick 104.
By the way, from among such operation controls of the different components as described above, for example, in order to revolve the upper revolving unit 102, an operator will first operate the lever 101B to start operation of the revolving motor 110.
Then, after the upper revolving unit 102 starts its revolving movement by a rotational driving force of the revolving motor 110, the operator will return the lever 101B to its neutral position before the upper revolving unit 102 is revolved to an aimed position. This is performed because an inertial force arising from the revolving movement acts upon the upper revolving unit 102 and because, if the lever 101B is returned to its neutral position after the upper revolving unit 102 is revolved to the aimed stopping position, then the actual stopping position passes the aimed stopping position.
Further, when the upper revolving unit 102 is revolved by an inertial force even if the operator returns the lever 101B to its neutral position in this manner, a crossover relief valve 120 disposed between the fluid path 113-5 of the revolving motor 110 operates to absorb the kinetic energy of the upper revolving unit 102.
This crossover relief valve 120 provides, when the revolving motor 110 is driven by the upper revolving unit 102 and the revolving motor 110 acts as a pump, resistance to the working oil discharged from the revolving motor 110 to absorb the kinetic energy of the upper revolving unit 102. Consequently, the crossover relief valve 120 has a function also as a resistor.
Further, the crossover relief valve 120 is a valve which is opened when the hydraulic pressure in the fluid paths 113-5 becomes higher than a predetermined pressure, and when the control valve 111-5 is in its neutral position and the revolving motor 110 is driven by the upper revolving unit 102, the working oil is circulated between the fluid path 113-5 and the revolving motor 110 via the crossover relief valve 120. In this instance, resistance acts upon the working oil by an action of the crossover relief valve 120 to absorb the kinetic energy of the upper revolving unit 102.
However, when such a crossover relief valve as described above is operated to stop revolution of the upper revolving unit, the kinetic energy of the upper revolving unit is discharged principally as thermal energy into the atmospheric air, and this is not always preferable from a point of view of effective utilization of energy.
Particularly, since an upper revolving unit of a construction machine has a counterweight placed at a position thereof spaced as far as possible from the center of revolving motion of the upper revolving unit in order to prevent the body from being tilted by a load upon working, the angular moment is high and the kinetic energy is high.
Therefore, it is demanded to effectively regenerate, when such an upper revolving unit as described above is to be stopped, the kinetic energy of the upper revolving unit to achieve effective utilization of the resources.
The present invention has been made to meet such a demanded as described above, and it is an object of the present invention to provide a control apparatus for a construction machine which can regenerate energy originating from an inertial force of a fluid pressure operated member of the construction machine to allow effective utilization of energy.